Ajit Kumar Mahapatra

Color response of tri-armed azo host colorimetric sensors and test kit for fluoride.

Five new chromogenic tripodal receptors (2a-e) containing electron withdrawing and donating groups appended to the azophenol moiety were synthesized, characterized, and their chromogenic behaviors toward various anions were investigated. These tripodal receptors showed a distinct color change only when treated with fluoride ions in CH(3)CN solution. Yet, other anions such as Cl(-), Br(-), I(-), NO(3)(-), ClO(4)(-), AcO(-), HSO(4)(-), and H(2)PO(4)(-) could not cause any color change. Thus, the receptors 2a-e can be used as a colorimetric chemosensor for the determination of fluoride ion. In addition, (1)H NMR experiments were carried out to explore the nature of interaction between tripodal receptors and fluoride. Finally, analytical application and the use of test strip of the receptor 2b to detect fluoride was also reported.

Ratiometric fluorescent and chromogenic chemodosimeter for cyanide detection in water and its application in bioimaging

An indole conjugated thiophene–pyridyl (ITP) sensor for cyanide has been synthesized and characterized using NMR and mass spectroscopy. The selectivity of ITP has been explored in aqueous solution, and the resulting ratiometric fluorescence response toward CN−, among 11 different anions, was studied. The complexation of ITP–CN has been addressed using HRMS, 1H-NMR, and UV-vis spectroscopy. ITP displays substantial dual changes in both its ratiometric emission and absorption spectra, exclusively in the presence of CN− in aqueous solution. This is due to the nucleophilic attack of the indolium group of ITP by CN−, which induces a ratiometric fluorescence change and consequently a large emission shift. DFT/TDDFT calculations were performed in order to demonstrate the electronic properties of ITP and the ITP–CN adduct. The resultant ITP–CN adduct was used as a secondary sensing chemo-ensemble for the detection of cyanophilic metal ion-containing molecules by removing CN− from ITP–CN and regenerating ITP with switch-on red fluorescence. For the practical application of the sensor, test strips based on ITP were made up, which could act as suitable and proficient kits for CN− testing and cell studies.

Colorimetric and ratiometric fluorescent chemodosimeter for selective sensing of fluoride and cyanide ions: tuning selectivity in proton transfer and C–Si bond cleavage

A simple innovative anthraimidazolyldione (LHSi) based colorimetric and ratiometric fluorescent chemodosimeter was designed and synthesized for fluoride and cyanide ion sensing. Upon reaction with the F− and CN− anions in THF solution, probe LHSi shows dramatic color changes from light yellow to red and remarkable ratiometric fluorescence enhancement signals. These properties are mechanistically ascribed to a fluoride/cyanide-triggered deprotonation and C–Si bond cleavage that resulted in a green to red fluorescence.

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions.

Summary A novel indolocarbazole-based chemosensor 1 containing hydrogen bond donor moieties has been established as a selective colorimetric and fluorometric sensor for F− in CH3CN/H2O (4:1 v/v). Upon the addition of a series of tetrabutylammonium salts to receptor 1 in aqueous CH3CN, only when the counter ion was F− was a significant color change (from light violet to dark orange) observed.

Unique Fluorogenic Ratiometric Fluorescent Chemodosimeter for Rapid Sensing of CN− in Water

A new benzimidazole-spiropyran conjugate chemosensor molecule (BISP) has been synthesized and characterized by (1)H NMR spectroscopy, mass spectrometry (ESI-MS), and elemental analysis. The two isomeric forms (BISP↔BIMC) were shown to be highly selective and sensitive to CN(-) among the ten anions studied in aqueous HEPES buffer, as shown by fluorescence and absorption spectroscopy and even by visual color changes, with a detection limit of 1.7 μM for BIMC. The reaction of CN(-) with BIMC was monitored by (1)H NMR spectroscopy, high-resolution mass spectrometry (HRMS), UV/Vis measurements, and fluorescence spectroscopy in HEPES buffer of pH 7.4. TDDFT calculations were performed in order to correlate the electronic properties of the chemosensor with its cyanide complex. Further, titration against thiophilic metal ions like Au(3+), Cu(2+), Ag(+), and Hg(2+) with [BIMC-CN] in situ showed that it acts as a secondary recognition ensemble toward Au(3+) and Cu(2+) by switch-on fluorescence. In addition, a reversible logic-gate property of BIMC has been demonstrated through a feedback loop in the presence of CN(-) and Au(3+) ions, respectively. Furthermore, the use of BIMC to detect CN(-) in live cells by fluorescence imaging has also been demonstrated. Notably, test strips based on BIMC were fabricated, which could serve as convenient and efficient CN(-) test kits.

Molecular Recognition Induced Supramolecular Array of 2-Aminopyrimidine with Terephthalic Acid, 1,4-Phenylenediacetic Acid and Fumaric Acid in Solid State via H-bonding and π-stacking Interactions*

Abstract The crystal structures of molecular complexes of 2-aminopyrimidine (2AP) with terephthalic acid (1) (1:1; Complex A), 1,4-phenylenediacetic acid (2) (1:1; Complex B) and fumaric acid (3) (1:2; Complex C) were determined. Complex A is orthorhombic, space group Pnma, with α = 13.0323(3), b = 23.9443(1), c = 3.7927(1) A α = β = γ = 90° Z = 4; Dcalc = 1.466 Mg/m3; final R = 0.0384, wR 2 = 0.0939 for 1381 independent reflections. Complex B is orthorhombic, space group Pben with α = 4.5686(1), b = 15.7687(2), c = 20.1621(4) A; α = β = γ = 90° Z = 4; Dcalc = 1.323 Mg/m3; final R = 0.0461, wR 2 = 0.1158 for 1662 independent reflections. Complex C is monoclinic, space group P21/c with α = 3.7946(2), b = 19.1766(7), c = 13.0641(6) A α = 90°, β = 96.893(1)°, γ = 90° Z = 4; Dcalc = 1.486 Mg/m3; final R = 0.0665, wR 2 = 0.1626 for 2752 independent reflections. 2AP generates supramolecular assembly with 2 and 3 via non-conventional weak C‒H‒O hydrogen bonding. Interestingly only in the case of Complex C, proto...

A BODIPY/pyrene-based chemodosimetric fluorescent chemosensor for selective sensing of hydrazine in the gas and aqueous solution state and its imaging in living cells

A BODIPY-based pyrenebutyrate-linked (BPB) chromogenic and fluorogenic probe was synthesized and characterized for the specific detection of hydrazine. In the presence of hydrazine, BODIPY-based pyrenebutyrate was selectively deprotected, producing switch off meso-phenoxyBODIPY along with a color change from yellow to brown, allowing colorimetric detection of hydrazine by the naked eye. Selectivity experiments proved BPB has excellent selectivity to hydrazine over other environmentally abundant ions and common amine-containing species. Probe BPB was also successfully applied in vapor hydrazine detection into a solid state over other interfering volatile analytes. Furthermore, the probe BPB coated with silica gel TLC plates could act as a visual and fluorimetric probe for hydrazine vapor detection. The probe (BPB) has been shown to detect hydrazine up to 1.87 μM at pH 7.4. DFT and TDDFT calculations were performed in order to demonstrate the sensing mechanism and the electronic properties of the probe and hydrazinolysis product. BPB can also be used for the detection of hydrazine in Vero cells without appreciable interference from other biologically abundant analytes.

A highly sensitive fluorescent probe for detection of hydrazine in gas and solution phases based on the Gabriel mechanism and its bioimaging

A new probe 2-benzo[1,2,5]thiadiazol-4-yl-isoindole-1,3-dione (BTI) based on the Gabriel reaction mechanism was synthesized and characterized for the specific detection of hydrazine with high selectivity against other amines in an organo-aqueous solution. Upon hydrazinolysis of BTI in the presence of hydrazine in a H2O–DMSO (4 : 6, v/v) solution (10 mM HEPES buffer, pH 7.4) at room temperature, the chemosensor produces fluorescent aminobenzthiadiazole with a maximum emission at 498 nm along with a color change from colorless to green, allowing selective colorimetric and fluorometric detection of hydrazine by the naked eye. Probe BTI was also successfully applied in vapor phase hydrazine detection into a solid state over other interfering volatile analytes. Furthermore, the probe BTI coated with silica gel TLC plates could act as a visual and fluorimetric probe for hydrazine vapor detection. The experimental detection limit of hydrazine is 2.9 ppb, which is well below the accepted limit (10 ppb) for hydrazine set by the U.S. Environmental Protection Agency (EPA). DFT and TDDFT calculations were performed in order to demonstrate the sensing mechanism and the electronic properties of probe and hydrazinolysis products. Additionally, probe BTI could also be applied for the imaging of hydrazine in living cells.

2-Aminopyrimidine-fumaric acid cocrystal

In crystals of the title compound, 2-aminopyrimidin-1-ium hemifumarate hemifumaric acid, C 4 H 6 N 3 + -0.5C 4 H 2 O 4 2- .0.5C 4 H 4 O 4 , the asymmetric unit contains one 2-aminopyrimidine cation, C 4 H 6 N 3 + , protonated at a pyrimidine ring-N atom, one half-molecule of fumaric acid, C 4 H 4 O 4 , and one half of a fumarate ion, C 4 H 2 O 4 2- . These are linked by N-H...O, O-H...O and relatively strong C-H...O bonds, resulting in eight- and nine-membered hydrogen-bonded rings and an extended supramolecular structure.

Aromatic aldehydes from benzylbromides via Cobalt(I) mediated benzyl radicals in the presence of aerial oxygen: a mild oxidation reaction in neutral condition

Abstract Co(PPh 3 ) 3 Cl has been shown to be a novel mediator for the conversion of benzylic bromides to aromatic aldehydes under mild conditions in the presence of aerial oxygen probably via benzylic radicals. In the absence of oxygen, the carbon-carbon coupling reactions have been utilised to afford a series of functionalised benzylic dimers.